Pump



Sept. 16,1930. G. M. cLAGETr 1,776,147

PUMP

med March so, 192e 40 lubricant being Patented sept. 1e,` 1930 GEORGE M.CLAGETT, or UPPER MARLBoRo, MARYLAND 'PUMP Application led March 30,1926. Serial No. 98,\554.

My invention relatesparticularly to air pumps such as are vused forinflating pneumatic tires but it is to .be understood that it is equallyapplicable to all other varieties .,5 of pumps having a reciprocatorypiston.

In my experience with the pumps of the prior art a number of diicultieshave 1nanifested themselves. In the first place the piston fails to takehold or catch the air un- A til after the'compression stroke is wellstarted. In other words there is a lost motion at the beginning of thecompression stroke. Also when it is sought to withdraw the pis` tonafter completing a compression stroke, I

have found that a vacuum is created in the outlet end of theV pistonchamber and this vacuum, of course, resists movement ofthe piston on itsreturn stroke until suficient air has leaked past the4 piston toovercome v `to the vacuum. This situation is particularly yobjectionablein l pumps` which involve a spring for effecting the return of thepiston to starting position after a compression stroke. I have alsoobserved that the leather `a5 piston washers or cups have a tendency,als

a vresult ofheatgenerated by reciprocations of the piston, yorotherwise, to become set,-that is to lose their flexibility and shrinkawayfrom the chamber walls. This,

0 of course, permits air to passv around the piston on a compressionstroke and the pump will not generate any pressure.l In' an attempt toovercome this tendencyto shrink or set, .considerable oil is keptV on`the L piston cup or washers as the case may be but even this fails toeffectively remedy the condition. The presence of lubricant inthe pistonchamber of an air-pump is manifestly objectionable due to the likelihoodof -the forced from the pump into the valve of the tire orotherreceptacle. v

,It is therefore the, object of my invention to overcome thel foregoingand other objections which manifest themselves inthe ytipumps ofthepriorarty and-.to producea had to th ,pump of simple,inexpensive anddurable construction which will give efficient service over a longperiod of time with but llittle Vor no attention. f

The various" features-of novelty which y characterize my invention arepointed out with particularity Yin the claims annexed to and forming apart of this specification. However, in order that the `invention may bebetter understood, reference should be e accompanying drawingillustrating what I now regard as the preferred embodiment. It is to beunderstood, of course, that I am vin nowise :limited to the illustratedform of the invention and that -30 Imay make such changes'andmodifications thereinas fairly fall within the spirit and scope of theclaims.

In the drawing, f

Figure l is a` perspective view embodying my improvements; v

Fig. 2 isa central longitudinal section,l and Fig. 3 is a cross sectionyof the line 33 of a pump Referringspecifically to the drawing, 4indicates a tubular casing having `one end threaded and screwed intoazbaseV 5. The other. endof the casing 4 is closed by means of a screwcap 6. Av piston rod 'Z vworking f through the cap 6 carries atits endlapiston generally denoted at 8 and which comprises a backingv disc 9,alleather pistoncup l() and a relatively smaller disc 10b. The assemblyis held together by meansofa nut l11 screwed upon the end of theextension 7a of the piston rod 7 ,the said extension passing throughcentral openings in the elements Y lof the piston as clearly showninFig. 2.

lThe major portion of the piston chamber S5 is denoted by 4a-and Fig. 2clearly illustrates that the upperend 4b of the chamber isldiametricallyvreduced. 'From the lower end ofthe reduced part 4", the.walls of the chamber taper outwardlythroughout a substantial portion ofthe length of the cylinder as indicated in 4. Thus, the piston chamber4a may be said to comprise three sections,- first a diametricallyreduced section, next an outwardly tapered section, and lastly anunreduced section the latter extending throughout the major portion ofthe length of the chamber, and at the end of which last named section aiiuid outlet is provided. The major portion 4a of the chamber isrelatively oversize as compared to the diameter of the piston,whil e therestricted part 4b is relatively smaller in diameter than usual as.compared with the diameter ofthe piston 8.

It is also to bel noted fromFig. 2 that the diameter of the backingdisk?) and the normal diameter ofthe piston cup 10 is suchas to snuglyfit in the reduced end 4b of the piston chamber. Thus, at the estart ofa com-r pression stroke the piston cup 1() will immediatelyV catch theair,thatiis to say there will ybe no initial escape of air aroundV theperiphery of the cup 10 as lis true in lcommon forms of pumps afterslight use. As the piston 8 is forced downwardly the air pressureagainst the bottom of the cup 10 vincreases and when the outwardlytapered section 4c of the chamber is reached the pressure beneath thecup 10 will besufficient to cause the wall 10a thereof to flexcircumferentially outward and be maintained in air-tight bearingengagement with the chamber wall. Manifestly this bearing engagementwill be continued throughout the remainderof the compression strokethrough the unreduced or slightly oversize part'4l of the chamber.

However, when the charge of air has been forced through thechamber therewill be no pressure beneath the cup 10J and the depending wall 10a willeither assume the full-lined position of Fig; 2 spaced from the cylinderwall, or will remain in anoutwardly flared state in but very lightengagement with the cylinder wall. Thus the instant the piston8 isstarted on its upstroke the pressure of air above will act upon theoutwardly flared area of the wall to move it inwardly to the full lineposition of Fig. 2. Viith the wall 10l of the piston cup clear of thechamberrwall it will be evident that the commencement of the air-intakeor return stroke of the piston 8 will be unretarded by any suctioncondition in the lower end of the chamber. i

yIn the (construction illustrated fandv` described itis obvious that buta minimum amount of heat will be generated by reciprocations of thepiston 8 for the reason that the cup wall 1()a is, broadly speaking, inengagement with the cylinder wall onlyfduring the compression stnoke. Asheretofore pointed out, in pumps of the prior art such heat as isgenerated by the piston rubbingagainst the cylinder wallwhile thepumps-are in use does much tocause the piston cup or washersto become'set, VthatV isto lose their resiliency and remain shrunk away from thechamber wall, also frequent lubrication fails to adequately remedy thecondition. Vith my construction not only is the heat reduced asheretofore pointed out, but in addition the movement of the pistonthrough the restricted,V tapered, and enlarged parts of the cylinder inthe normal operation of the pump, causes the effective part of thepiston cup, namely the wall 10a, to be repeatedly flexed. The wall 10nof the piston cup is thus exercised, so to speak, and is prevented frombecoming stiffened, or \set. Little or no lubrication is required tokeep the cup A walll()a in a flexiblestateowing to this exercising towhich it is subjected, and also in a lesser degree to the fact that itstendency to stiffen or set is greatly reduced owing to the absence ofthat,4` high degree of heat which is generated by pistons which4constantly engage the walls of their cylinders."

The base 5, as shown in F-ig. 2has a medial bosslike part 12 vwith acentralrecess 12u in alinement with the nut 11 and of a size toaccommodate the latter. The heightV of Y the boss 12 is less than thewidth of the wall 10a of the cup 1() and surrounding the boss is agroove 13 designed to receive the cup wall 10a. Since the depth of thegroove 13 isless than the width of the cup wall 10a,`the latterl acts asa cushion and prevents the piston 8 from being banged against the boss.V-Furtliermore, the pressing of the piston so as to engage the edgepart'of the piston'fcup Wall 10a in the bottom of the groove'13v furtherflexes or exercises said wall to keep itin iiexible condition. f y i yOutlet from lthe pump is had through a port in the end of the casing 4which establislies communication between the pistonv chamber4a and aduct14 which is formed in the base and has communication with a'valvechamber 15 which is formed in an enlargement 16 of the base. A ballvalve 17 backed by a'spring 18 and a screw'pluf`r19 normallyf= acts toseal the mouth of the duct 14. V The screw plug 19 is also the closurefor the valve' chamber 15. The forcing of the air into the duct 14raises the'ball valve 17 'and permits the air topass out through thenipple 2O into the vhose connection 21.

Having thus` described my invention, what I claim is: A y p f Y 1. Apump having a'compression chamber restricted at its lintake end andenlarged throughout the Vmajor portion of itslengtl'i and at its outletend, the portion -offsaid chamber intermediate Vsaid restrictedandenlarged portions'having its walls'tapered,fa piston working in'saidchamber and of anormal* diameterto snugly' fit in the restricted end ofsaid chamber, a flexible? peripheral part carried by said pistonresponsive to fluid pressure on the compression' stroke to moveradiallyL outward and engage; the walls ofv said izo chamber whereby toeffect a seal thereat as the piston moves through the tapered andenlarged part of the chamber, and said peripheral part on completion ofsaid compression stroke and the discharge of said fluid assuming itsnormal position clear of said chamber walls.

2. A pump having a piston chamber' and a reciprocatory piston workingtherein, a circumferentially expansive element carried by said piston,said chamber having a constricted part of substantial length to causesaid element to snugly engage the chamber wall at the commencement of aworking stroke to prevent escape of fluid, the normal diameter of saidpiston being less than the diameter of the major lportion of saidchamber, and the pressure of the fluid after the piston has moved fromthe constricted part of said chamber acting upon said circumferentiallyexpansive element to cause the same to bear against the chamber wallthroughout the remainder of its stroke.

3. A pump having a piston chamber and a flexible piston element workingtherein, said chamber having a diametrically reduced piston receivingportion extending from an end of the chamber to a point well withinv themaximum stroke limit of the piston.

4. A pump having a piston chamber and a flexible piston element workingtherein, said chamber having a portion of its bore adjacent one enddiametrically reduced within the maximum stroke limit of the piston andin unbroken continuity with the remainder of the chamber bore.

v 5. A pump having a piston chamber and a i flexible piston elementworking therein, said chamber having a continuous unbroken bore from endto end and having a diametrically reduced portion within the maximumstroke limits of the piston.

6. A pump having a piston chamber and a iexible piston element workingtherein, said chamber having a continuous smooth bore from end to endwithin the maximum stroke limits ofthe piston; and a portion of saidbore being reduced in cross-sectional area over a considerablelongitudinal extent vof the piston chamber but terminating ata pointshort of the position occupied by the piston at the completion of itscompression stroke.

7. In a reciprocatingv piston pump, a flexible piston and a workingchamber therefor, said-chamber having an unbroken wall and being formedwith a cross-sectionally reduced piston confining area, a piston releasearea of unreduced cross-section, and a. flared intermediate pistonexpansion limiting area.

8. In a reciprocating piston pump, the combination with a flexiblereciprocatory piston, of a chamber therefor having a smooth consaidreduced end and the remainder of the chamber. v

In testimony whereof I aiiix my signature.

GEORGE M. CLAGETT.

tinuous and unbroken working bore from end Y to end, said bore beingdiametrically reduced

